North Korea has forged ahead in developing ballistic missiles, testing new capabilities, honing existing weapons and putting them into service. All of this work was accompanied by an explicit, repeated message that it would never abandon its arsenal.

After historic denuclearisation talks between leader Kim Jong Un and U.S. President Donald Trump fell apart in 2019, Pyongyang rolled out new and increasingly capable short-range ballistic missiles (SRBMs), many of which can manoeuvre to confound missile defences.

It then unveiled and tested more advanced weapons, including "hypersonic" missiles, SRBMs for “tactical” nuclear attacks, new submarine launched ballistic missiles (SLBMs), and its largest ever intercontinental ballistic missile (ICBM), which eventually may be able to rain nuclear warheads on multiple targets almost anywhere on the planet.

The record-setting March test was nearly matched by another ICBM launch in November that also soared more than 6,000 kilometres (3,728 miles) into space.

Like most North Korean long-range ballistic missile tests, both ICBMs were fired on lofted trajectories. Pyongyang says it does this out of concern for the safety of its neighbours.

It has now fired at least three intermediate-range ballistic missiles (IRBMs) over Japan, however, including the Oct. 4, flight, where the missile - possibly a variant of the intermediate-range Hwasong-12 - landed about 3,200 km beyond Japan in the Pacific Ocean.

Trajectories of some of North Korea’s long-range missile tests

Nuclear warheads

South Korea and the United States have warned since early 2022 that North Korea may resume nuclear testing for the first time since 2017. Analysts say that could help it perfect smaller nuclear warheads that can fit on a range of missiles.

"Kim announced plans to develop weapons systems ranging from tactical nuclear weapons to a nuclear-powered submarine and is ticking the boxes on his weapons wishlist through a series of tests," Hwang Ildo, of Seoul's Institute of Foreign Affairs and National Security, said in a recent report.

One focus has been “tactical” nuclear weapons, whose warheads have less explosive power but are meant for battlefield use, attacking specific targets relatively close to the launch point.

Targeting U.S. bases in South Korea with such weapons makes sense because the North Korean military does not have enough conventional warheads to meaningfully damage such facilities and prevent a conventional U.S. strike on North Korea, said Duyeon Kim, a North Korea expert at the U.S.-based Center for a New American Security.

“It would now be able to do so, while reserving its ICBMs and thermonuclear bombs to deter the United States from retaliatory annihilation of North Korea,” she said.

Despite their short range, tactical nuclear weapons are particularly dangerous because they can evade missile defences and are meant for combat - making their use more likely than their larger brethren, Kim said.

“Their purpose is to use them on the battlefield during a conflict, to quickly end a conflict, or to deter the U.S. and South Korea from waging a military campaign against the North,” she added.

Re-entry vehicles

Launching missiles into space is a critical first step for a weapons programme, but the warheads they carry must survive the fiery re-entry through Earth’s atmosphere and accurately strike targets.

Ankit Panda of the United States–based Carnegie Endowment for International Peace said that testing with a more realistic trajectory, such as the Oct. 4 IRBM launch over Japan, allows North Korea to expose a reentry vehicle to temperatures and stresses that are more representative of what they'd endure in real-world use. He added, however, that North Korean scientists appear to have only a limited ability to collect data from rockets that land far away.

North Korea also claims to have tested a new type of "hypersonic missile" in late 2021 and in 2022. Such weapons usually fly at lower altitudes than typical ballistic missiles at more than five times the speed of sound - or about 6,200 kph (3,850 mph).

Analysts say the main feature of hypersonic weapons is not speed but the ability to manoeuvre, which can help them avoid interception and even switch targets after launch.

How hypersonic missiles avoid interception

"One particular theme over the last couple of years is the further diversification of delivery systems to provide additional challenges for regional missile defence, particularly the use of quasi-ballistic trajectories, experimenting with claimed hypersonic glide vehicles as well as cruise missiles," said Joseph Dempsey, a defence researcher at the International Institute for Strategic Studies.

In its annual threat assessment this year, the U.S. intelligence community said Kim was prioritising efforts to build a capable missile force that could evade U.S. and regional defences.

In November, Pentagon spokeswoman Sabrina Singh said she couldn’t speculate about whether the Hwasong-17 could hit the mainland United States.

Pyongyang says its weapons are for self defence and are necessary to counter the military threats of the United States and its allies. In a new nuclear policy law enacted in September, it outlined an expansive vision for their potential use, including the threat of an imminent nuclear strike; if the country's leadership, people or existence were under threat; or to gain the upper hand during a war.

“North Korea’s missiles pose an increased threat to our country,” said Kwon Ki-hyun, a spokesman for South Korea’s Ministry of National Defense.

To counter those threats, South Korea is strengthening and developing its so-called “three-axis system” and other defensive measures, he said, referring to the country’s strike, air defence, and retaliation capabilities. Seoul plans to spend about 30 trillion won ($21 billion) on enhancing the system over the next five years.

Manoeuvres during flight

Analysts say that the increasing size of North Korean missiles as well as work on what the country says is technology for controlling its satellites in orbit suggests Pyongyang is looking to arm its ICBMs with multiple, manoeuvrable nuclear warheads and decoys.

"When a missile is designed to carry multiple warheads, three or four warheads detach from the rocket and re-enter the Earth’s atmosphere to glide to its target - a capacity that would make it much harder for U.S. missile defences to intercept," Hwang wrote.

Some North Korean claims are disputed. South Korean intelligence officials have cast doubts on the capabilities of the hypersonic missiles tested this year, saying they did not seem more advanced than existing designs.

After the March ICBM test, which North Korea claimed was its massive new Hwasong-17, South Korean and U.S. officials said it appeared to have been an older Hwasong-15. South Korea also reported that several missiles appeared to fail mid-flight, including an apparent Hwasong-17 that exploded over Pyongyang in March.

Multiple re-entry vehicles

Two-track testing

Before Kim Jong-un assumed office in 2012, North Korea had test fired only two different kinds of ballistic missiles in 31 launches between 1984 and 2009.

Kim Jong-un started firing missiles a year after assuming office. The country has since tested a dozen different kinds of missiles of many sizes and types. The rate of testing has increased as well – North Korea launched nearly five dozen ballistic missiles in 2022, the most in one year.

Pyongyang had declared a self-imposed moratorium on long-range test launches from 2018 until March 2022. During that break, however, it was far from quiet, rolling out new smaller systems such as SRBMs.

"What continues to stand out is the sheer number of new missile designs that continue to emerge from North Korea," Dempsey said.

Some designs seem to overlap, which could mean North Korea is simply trying as many options as possible rather than fully testing, manufacturing, and deploying them in meaningful numbers, he added.

Many of North Korea's most recent SRBMs, such as its KN-23 and KN-24, are designed to fly on a lower, "depressed" trajectory and potentially manoeuvre, complicating efforts to detect and intercept them.

Although long-range testing gains North Korea international attention, short-range weapons help it prepare for a potential confrontation with its neighbours, especially South Korea, which hosts about 28,500 American troops. In its testing programme, short-range missiles seem to have been the most successful.

Success rate of North Korea’s ballistic missile launches

Shifting launch sites

Recent years have seen North Korea test missiles from different locations and launch platforms in what analysts say is an effort to simulate a conflict and make it difficult for enemies to detect and preemptively destroy the weapons.

Missile launch locations

Since 2019, North Korea has tested the KN-23 from nine different locations, the KN-24 from four different locations and the KN-25 from seven different locations.

In January North Korea launched two SRBMs from a train near the northern border with China, in what state media said was a short-notice drill aimed at boosting the proficiency of the troops operating the missiles.

Despite the country's limited and sometimes unreliable rail network, rail-mobile missiles are a relatively cheap and efficient option to improve their survivability, analysts say.

Same missiles, different locations

Among North Korea's ballistic missiles, SRBMs appear to be the most likely to be deployed, Panda said.

"Since 2019, we've seen certain missiles, like the KN-23 especially, tested quite a few times, exhibiting a test and operational exercise pattern that suggests a serious interest in improving the overall reliability and military utility of this system," he said.

The KN-23, which can reach anywhere in South Korea, has been fired from a road-based launch vehicle, a rail car, and an experimental submarine. North Korea has promised that an operational missile submarine will soon be deployed.

Submarine-launched ballistic missiles (SLBMs) could give North Korean forces increased reach plus an additional element of surprise. They could also be an additional option if land-based launch sites are destroyed.

Fuel and engines

North Korea's SRBMs and SLBMs are test beds for developing another key rocket technology: solid fuel.

Most of the country's largest ballistic missiles use liquid fuel, which typically requires them to be loaded with propellant at their launch site - a time-consuming step that makes them easier to spot and destroy.

The U.S. government says ingredients for solid propellant, including aluminium powder and ammonium perchlorate, are among the top items sought by the overseas procurement agents who help supply North Korea’s weapons programmes.

“There is some debate about whether North Korea can indigenously manufacture the components (for missile engines) or whether they rely on third parties, like China or Russia,” said Aaron Arnold, a former sanctions investigator now with the the RUSI think-tank in London.

So far, most of North Korea’s solid-fuel engines have been used on smaller, short-range missiles, and recent tests suggest military scientists are experimenting with a third option: a "missile fuel ampoule" system that seals the liquid propellant and oxidizer in tanks inside the missile at the factory.

The volatility of that fuel-storage system casts doubt on its military usefulness, however, with some analysts likening it to "driving around with a bomb".

That leaves solid fuel as an attractive goal for North Korea. On Dec. 16, scientists there tested what they called a “high-thrust” solid-fuel motor that appeared aimed at perfecting a large engine for an ICBM.

"One of Kim Jong Un's objectives... is to develop an ICBM propelled by solid-fuel engines, and if North Korea succeeds, it will become difficult for the U.S. to defend against Pyongyang’s nuclear arsenal, as signs of an ICBM launch using solid-fuel engines are hard to detect early," Hwang wrote.